Sen. Susan Collins' office says she'll make an announcement on Friday about whether she'll run for governor of Maine.
The moderate Republican was first elected in 1996 and has played a pivotal role in the Senate in recent debates about health care policy. She said previously that she would decide during the Senate's weeklong Columbus Day recess whether to stay in Washington or run for governor.
Collins' office did not say where the senator would make the much-anticipated announcement.
Republican Gov. Paul LePage is term-limited, and the election to replace him is in 2018.
LePage is an ally of President Donald Trump, whom Collins has publicly criticized in the past. LePage and Collins have also disagreed about the best path forward on health care.